1. Field of the Invention
This invention relates to certain improvements in the card racks used to support printed circuit cards while said cards are inserted in mating connector blocks.
2. Description of the Prior Art
The closest art of which inventor is aware is contained in U.S. Pat. Nos. Re. 25,595; 3,311,863; and 3,197,731. These patents all disclose card rack apparatus employing card guides having slots into which opposite edges of the card to be held fit and slide to a mating position in which electrical contact is made between the circuitry on the card and the connector block. There are other references cited in connection with the prosecution of U.S. Pat. No. Re. 25,595, notably U.S. Pat. Nos. 3,008,113; 2,951,185 and 2,731,609 which also disclose card type circuit modules mounted in slotted retainers facilitating insertion and removal of individual cards.
Because of decreases in cost and size of individual logic elements, the trend is to place larger numbers of individual elements on each printed circuit card than has been previously practiced. This results in the necessity for a larger number of more closely spaced connections between the card and the connector block associated with it. Because of the larger number of interconnections between each block and its card, individual contacts have of necessity become smaller, more numerous, and more closely spaced. This in turn has required increased precision in aligning the card with the connector block when inserting the card into mated position. Because of the increased force necessary to mate the larger number of contacts on an individual card, it is not always possible when inserting the card to sense whether or not it is accurately positioned just prior to the individual contacts entering their respective sockets. Improper card positioning in this case results in bent and damaged pins, if pin contacts are used, and improper electrical connections. Therefore, it is desirable to position the card just prior to entry of the pins contacts to their respective sockets more accurately than has been heretofore conveniently possible.